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My understanding is that this is not exactly a GUI client.

You can give pgXplorer (http://pgxplorer.com) a shot which is open source and the binaries are readily available. Disclaimer: I am the lead dev of pgXplorer.

The good news is that the Sequel Pro guys have started to work on their Postgres framework:

http://stuconnolly.com/blog/sequel-pro-postgresql-support/

What's wrong with PgAdmin?

No, I don't count 'not looking native' as a problem.

I've had a good experience with Tuple: http://www.tuplesapp.com/

its not Sequel Pro but you can try http://inductionapp.com

It's a great app, but for different purpose. Induction is mainly for viewing/analyzing _data_, where pgAdmin, while horrible looking, is for managing database schema.

See my link for DbVisualizer.